Conventionally, a remote control technology is widely used in which a computer (server device) that is provided in a remote place on a network is operated using a computer at hand (client device). VNC (Virtual Network Computing) transmits image information of the server device to the client device using the RFB (Remote Frame Buffer) protocol, and displays the image information on a display screen of the client device.
As an example, the client device transmits operation information of a mouse, a keyboard, and the like, to the server device. The server device generates a moving image on the basis of the operation information. Then, the server divides the generated moving image into frames that are reproduction units at every fixed time (e.g., 0.1 second). The divided frames are sequentially converted into packets, but usually, a difference from a previous frame is converted into a packet. Then, the server device sequentially transmits the converted packets to the client device. The client device reproduces a moving image from the received packets, and displays the moving image on the display screen.
In addition, a technology is disclosed in which, in a thin client system that is constructed such that a client device has minimum functions and a server device manages resources, such as applications or files, an image in an image memory of the server device is divided into a plurality of regions, a frequency of change between frames is determined for each of the regions, a region in which the frequency of change exceeds a threshold value is identified as a high-frequency update region, a moving image compression process with a higher compression ratio is performed on the image of the identified region, and the image is transmitted (see, for example, Patent Document 1).
In addition, a technology is disclosed in which, in an image capturing device and a moving image distribution system capable of managing a construction site from a remote place by distributing a situation of a road construction site using a moving image, still images are extracted and generated that constitute a moving image at the time of receiving a still image transmission request signal in response to the still image transmission request signal (see, for example, Patent Document 2).
Patent Document 1: Japanese Laid-open Patent Publication No. 2011-238014
Patent Document 2: Japanese Laid-open Patent Publication No. 2010-220189